[ARM] clkdev: fix clock matching

The old matching algorithm was too fuzzy, causing false positives.
For example, when asked for device D connection C1 and we only find
device D connection C2, we return that as a valid match despite the
connection names being different.

Change the algorithm such that:
  An entry with a NULL ID is assumed to be a wildcard.
  If an entry has a device ID, it must match
  If an entry has a connection ID, it must match

However, we maintain the order of precidence while still only doing
a single pass over all entries: dev+con > dev only > con only.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>